The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Scroll compressors may be used in a wide variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically “refrigeration systems”) to provide a desired heating or cooling effect. A scroll compressor may incorporate a pair of intermeshed spiral wraps, or scroll members, one of which orbits with respect to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port towards a center discharge port. An electric motor may drive the orbiting scroll member.
Compressor capacity may be modulated according to refrigeration system load to increase compressor efficiency. For example, capacity modulation may be accomplished by a scroll separation system that separates the two scroll members to create a leak path and unload the compressor for predetermined periods of time. The leak path may be created by axial or radial separation of the scroll members. A scroll compressor with a scroll separation system that unloads the compressor by separating the scroll members is described in U.S. Pat. No. 6,213,731, the disclosure of which is incorporated herein by reference.
Capacity modulation may also be accomplished by a delayed suction system that utilizes ports provided at one or more positions which, when opened with valves, allow the initially formed compression chamber between the scroll members to communicate with the suction chamber of the compressor. Opening the ports creates a leak path between the initially formed compression chamber and the suction chamber to unload the compressor. This delays the point at which the sealed compression chambers are formed and, thus, delays the start of compression. A scroll compressor with a delayed suction system that modulates compressor capacity by venting an intermediate pressurized chamber to the suction chamber is described in U.S. Pat. No. 6,821,092, the disclosure of which is incorporated herein by reference.
Capacity modulation may also be accomplished by a refrigerant injection system that injects refrigerant at a higher pressure than the suction pressure into the suction chamber or into one or more intermediate pressurized moving chambers between the scroll members. Compressor capacity may be increased, as compared with normal compressor capacity, by injecting the higher pressure refrigerant. A scroll compressor with a refrigerant injection system is described in U.S. Pat. No. 6,619,936, the disclosure of which is incorporated herein by reference.
Traditional capacity modulation systems, however, may result in inefficient energy usage or consumption. For example, when compressor capacity is decreased with a capacity modulation system, the compressor may continue to consume power while operating during the time the compressor is unloaded. The unloaded compressor may continue to consume power although the unloaded compressor is not compressing or circulating refrigerant.